/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/ShapeFunctions.h
Compute the pair of closest points on a 3D Ray and Line. The Line is defined by an Origin and Direction (ie same as a Ray) but extends infinitely in both directions.
the minimum distance between the Ray and Line, ie between RayPoint and LinePoint
static double GetRayLineClosestPoint ( FRay Ray, FVector LineOrigin, FVector LineDirection, double & RayParameter, FVector & RayPoint, double & LineParameter, FVector & LinePoint )